Driving assistance apparatus and driving assistance method

ABSTRACT

Provided is a driving assistance apparatus configured to determine whether or not an own vehicle driving lane is a merging lane based on a result of identifying the merging lane from a lane reduction sign detected in a vehicle front image and a result of identifying a merged lane direction with respect to the own vehicle driving lane from separation lines on both sides of the own vehicle driving lane that are detected in the vehicle front image, and to control driving of an own vehicle in accordance with the determination result and vehicle condition information of the own vehicle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a driving assistance apparatus and adriving assistance method for providing appropriate driving assistanceto a driver of a vehicle traveling on a merging lane.

2. Description of the Related Art

Hitherto, there have been proposed a large number of driving assistancetechnologies for avoiding traffic accidents of automobiles by givingassistances to drivers' function such as recognition, decision, oroperation (for example, see Japanese Patent Application Laid-open No.2005-352636 and Japanese Patent Application Laid-open No. 2014-44744).Specific examples of the above-mentioned driving assistance technologiesinclude the following control.

First, there is known Adaptive Cruise Control (ACC) control, in which acamera or the like installed in a vehicle is used to keep a distancebetween an own vehicle and a forward vehicle at a certain length orlonger and at the same time maintain a vehicle speed at a set speed.Secondly, there is known Lane Keep Assist (LKA) control, in whichseparation lines of a driving lane on which the vehicle is traveling aredetected and a driver's steering wheel operation is assisted based onthe detection result. Thirdly, there is known Lane Departure Warning(LDW) control, in which the driver is warned of a possibility of thevehicle departing from the driving lane when such a possibility exists.

SUMMARY OF THE INVENTION

Then, when the ACC control is performed in a case where there is novehicle ahead of the own vehicle because the forward vehicle has justchanged a merging lane while the own vehicle is traveling on that lanein a lane reduction situation of a road, there is a possibility of theown vehicle performing an acceleration operation. Thus, in this case, itis necessary to prevent the acceleration operation of the own vehicle.

Further, in a case where the own vehicle is traveling on the merginglane, the LKA control and the LDW control need to be continued when theown vehicle continues to travel on the merging lane, whereas the LKAcontrol and the LDW control need to be prohibited when the own vehicleis merging into a merged lane from the merging lane.

In this way, it is necessary to provide appropriate driving assistanceto the driver of a vehicle traveling on a merging lane.

The present invention has been made to address the above-mentionedchallenges, and has an object to acquire a driving assistance apparatusand a driving assistance method capable of providing appropriate drivingassistance to the driver of a vehicle traveling on a merging lane.

According to one embodiment of the present invention, there is provideda driving assistance apparatus including: an image pickup unitconfigured to generate a vehicle front image by picking up an image of afront field of an own vehicle traveling on an own vehicle driving lane;a merging lane identification unit configured to detect a lane reductionsign in the vehicle front image generated by the image pickup unit,identify a merging lane based on the lane reduction sign, and generatean identification result as merging lane information; a merged lanedirection identification unit configured to detect separation lines onboth sides of the own vehicle driving lane in the vehicle front imagegenerated by the image pickup unit, identify a merged lane directionwith respect to the own vehicle driving lane based on the separationlines on both sides, and generate an identification result as mergedlane direction information; an own vehicle driving lane determinationunit configured to determine whether or not the own vehicle driving laneis the merging lane based on the merging lane information generated bythe merging lane identification unit and the merged lane directioninformation generated by the merged lane direction identification unit;a vehicle condition detection unit configured to detect vehiclecondition information of the own vehicle; and an own vehicle drivingcontrol unit configured to control driving of the own vehicle inaccordance with the vehicle condition information detected by thevehicle condition detection unit and a result of determination by theown vehicle driving lane determination unit.

Further, according to one embodiment of the present invention, there isprovided a driving assistance method, including: an image pickup step ofgenerating a vehicle front image by picking up an image of a front fieldof an own vehicle traveling on an own vehicle driving lane; a merginglane identification step of detecting a lane reduction sign in thevehicle front image generated in the image pickup step, identifying amerging lane based on the lane reduction sign, and generating anidentification result as merging lane information; a merged lanedirection identification step of detecting separation lines on bothsides of the own vehicle driving lane in the vehicle front imagegenerated in the image pickup step, identifying a merged lane directionwith respect to the own vehicle driving lane based on the separationlines on both sides, and generating an identification result as mergedlane direction information; an own vehicle driving lane determinationstep of determining whether or not the own vehicle driving lane is themerging lane based on the merging lane information generated in themerging lane identification step and the merged lane directioninformation generated in the merged lane direction identification step;and an own vehicle driving control step of controlling driving of theown vehicle in accordance with vehicle condition information of the ownvehicle and a result of determination in the own vehicle driving lanedetermination step.

According to the one embodiment of the present invention, the drivingassistance apparatus is configured to determine whether or not the ownvehicle driving lane is the merging lane based on the result ofidentifying the merging lane from a lane reduction sign detected in avehicle front image and the result of identifying the merged lanedirection with respect to the own vehicle driving lane from theseparation lines on both sides of the own vehicle driving lane that aredetected in the vehicle front image, and to control the driving of theown vehicle in accordance with the determination result and the vehiclecondition information of the own vehicle. With this, it is possible toacquire the driving assistance apparatus and the driving assistancemethod capable of providing appropriate driving assistance to the driverof a vehicle traveling on a merging lane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block diagram for illustrating a driving assistanceapparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram for illustrating a first example of a lanereduction sign to be detected by a merging lane identification unit ofFIG. 1.

FIG. 3 is a schematic diagram for illustrating a second example of thelane reduction sign to be detected by the merging lane identificationunit of FIG. 1.

FIG. 4 is a schematic diagram for illustrating a third example of thelane reduction sign to be detected by the merging lane identificationunit of FIG. 1.

FIG. 5 is a schematic diagram for illustrating a fourth example of thelane reduction sign to be detected by the merging lane identificationunit of FIG. 1.

FIG. 6 is a schematic diagram for illustrating a fifth example of thelane reduction sign to be detected by the merging lane identificationunit of FIG. 1.

FIG. 7 is a schematic diagram for illustrating a sixth example of thelane reduction sign to be detected by the merging lane identificationunit of FIG. 1.

FIG. 8 is an explanatory diagram for illustrating a method ofidentifying a merged lane direction to be performed by a merged lanedirection identification unit of FIG. 1.

FIG. 9 is a flowchart for illustrating a series of operations to beperformed by the driving assistance apparatus according to the firstembodiment of the present invention.

FIG. 10 is a flowchart for illustrating the series of operations to beperformed by the driving assistance apparatus according to the firstembodiment of the present invention.

FIG. 11 is an overall block diagram for illustrating a drivingassistance apparatus according to a second embodiment of the presentinvention.

FIG. 12 is a flowchart for illustrating a series of operations to beperformed by the driving assistance apparatus according to the secondembodiment of the present invention.

FIG. 13 is a flowchart for illustrating the series of operations to beperformed by the driving assistance apparatus according to the secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a description is given of a driving assistance apparatus and adriving assistance method according to preferred embodiments of thepresent invention with reference to the drawings. Note that, in thedescription of the drawings, the same or corresponding parts are denotedby the same reference symbols, and an overlapping description thereof isomitted.

First Embodiment

FIG. 1 is an overall block diagram for illustrating a driving assistanceapparatus according to a first embodiment of the present invention. Thedriving assistance apparatus of FIG. 1 includes an image pickup unit 1,a driving assistance control unit 2, a vehicle condition detection unit3, and a forward vehicle detection unit 4. In FIG. 1, an engine controlunit 5 and a brake control unit 6 to be controlled by the drivingassistance control unit 2 are illustrated together with theabove-mentioned components.

The image pickup unit 1 picks up an image of a front field of an ownvehicle traveling on an own vehicle driving lane to generate and outputa vehicle front image. The image pickup unit 1 is formed of, forexample, one or a plurality of cameras. Further, for example, an opticalcamera or an infrared camera may be used as the camera.

The driving assistance control unit 2 is realized by a processingcircuit such as a CPU executing a program stored in a memory or a systemLSI. The driving assistance control unit 2 includes a merging laneidentification unit 21, a merged lane direction identification unit 22,an own vehicle driving lane determination unit 23, and an own vehicledriving control unit 24.

The merging lane identification unit 21 performs an image analysis on avehicle front image acquired from the image pickup unit 1, to therebydetect a lane reduction sign for indicating lane reduction in an ownvehicle traveling road.

Now, a description is given of examples of the lane reduction sign withreference to FIG. 2 to FIG. 7. FIG. 2 to FIG. 7 are schematic diagramsfor illustrating the first to the sixth examples of the lane reductionsign to be detected by the merging lane identification unit 21 of FIG.1, respectively.

Respective figures of FIG. 2 to FIG. 5 are illustrations of variouskinds of traditional road signs for indicating lane reduction ahead inthe road. For example, FIG. 2 is an illustration of a road sign forindicating that a left lane is the merging lane out of the left lane, acenter lane, and a right lane in a road, and that the number of lanes isdecreased from three to two ahead in the road.

Respective figures of FIG. 6 and FIG. 7 are illustrations of variouskinds of construction signs for indicating lane reduction ahead in theroad due to an ongoing road work. For example, FIG. 6 is an illustrationof a construction sign for indicating that a left lane is the merginglane out of the left lane and a right lane in a road, and that thenumber of lanes is decreased from two to one 200 m ahead in the road.

As described above, it is possible to identify the number of lanes in aroad and also identify which lane out of lanes in the road is themerging lane, namely, the position of the merging lane based on theshape of a figure depicted in the lane reduction sign for indicating thelane reduction.

The merging lane identification unit 21 identifies the merging lanebased on the shape of a figure depicted in the lane reduction sign thathas been detected from the vehicle front image. Specifically, themerging lane identification unit 21 identifies the number of lanes andthe position of the merging lane in the road. Further, the merging laneidentification unit 21 generates the identification result as merginglane information, and outputs this merging lane information.

In this case, for example, the following method is conceivable as aspecific method of identifying the number of lanes and the position ofthe merging lane in the road to be performed by the merging laneidentification unit 21.

That is, this method performs sobel filtering on the vehicle front imagein each direction, and detects a triangle as a road sign candidate or arectangle as a construction sign candidate from edge points. Then, thismethod performs pattern matching on the detected region with referenceto road sign templates or construction sign templates that are stored ina storage unit (not shown) in advance, to thereby be able to identifythe number of lanes indicated by the road sign or the construction signand the position of the merging lane. Note that, the storage unit maystore in advance lane reduction sign templates that may exist in Japanor in foreign countries as well as the lane reduction signs illustratedin FIG. 2 to FIG. 7 as templates for performing pattern matching.

Through configuration of the merging lane identification unit 21described above, it is possible to accurately identify which of the leftand right lanes is the merging lane. Further, it is possible toaccurately identify the merging lane even when map information such asthat of an automotive navigation system does not allow the lanereduction to be grasped such as when the map information is obsolete orthe number of lanes is temporarily decreased due to a work.

The merged lane direction identification unit 22 performs an imageanalysis on the vehicle front image acquired from the image pickup unit1, to thereby detect separation lines on both sides of the own vehicledriving lane. Specifically, the merged lane direction identificationunit 22 detects the positions of the separation lines on both sides ofthe own vehicle driving lane on which the own vehicle is traveling andline types of those separation lines. Further, the merged lane directionidentification unit 22 generates the detection result as separation lineinformation, and outputs this separation line information.

Further, the merged lane direction identification unit 22 identifies amerged lane direction with respect to the own vehicle driving lane basedon the line types of the separation lines on both sides of the ownvehicle driving lane contained in the separation line information,generates the identification result as merged lane directioninformation, and outputs this merged lane direction information.

Now, a description is given of a specific method of identifying themerged lane direction with respect to the own vehicle driving lane to beperformed by the merged lane direction identification unit 22 withreference to FIG. 8. FIG. 8 is an explanatory diagram for illustratingthe method of identifying the merged lane direction to be performed bythe merged lane direction identification unit 22 of FIG. 1. Note that,in FIG. 8, a case is exemplified in which a left lane in the road is themerging lane and a center lane is the merged lane.

When separation lines on both sides of the own vehicle driving lane arefocused, as can be seen from FIG. 8, the line type of one of theseparation lines on both sides of the merging lane that is on the mergedlane side, namely, the line type of the separation line separating themerging lane from the merged lane is a broken line, whereas the linetype of the other of the separation lines on both sides is a solid line.

Thus, when the detected line type of one of the separation lines on bothsides of the own vehicle driving lane is a broken line, whereas theother is a solid line, the merged lane direction identification unit 22determines that the own vehicle driving lane has a possibility of beingthe merging lane and identifies the direction toward the separation linehaving the line type of a broken line as the merged lane direction.

On the other hand, when the line types of the separation lines on bothsides of a lane are both broken lines or solid lines, the lane is notthe merging lane. Thus, when the detected line types of the separationlines on both sides of the own vehicle driving lane are both brokenlines or solid lines, the merged lane direction identification unit 22determines that the own vehicle driving lane has no possibility of beingthe merging lane and identifies “none” as the merged lane direction.

In this way, the merged lane direction identification unit 22 canidentify the merged lane direction with respect to the own vehicledriving lane based on the combination of the line types of theseparation lines on both sides of the own vehicle driving lane.

Note that, as the method of identifying the merged lane direction to beperformed by the merged lane direction identification unit 22, themerged lane direction may be identified through identification of whichlane of lanes in the road the own vehicle driving lane on which the ownvehicle is currently traveling is, based on positional information withan accuracy of several centimeters that is acquired from a GPS or aquasi-zenith satellite and map information that is stored in the storageunit in advance.

The own vehicle driving lane determination unit 23 determines whether ornot the own vehicle driving lane is the merging lane based on themerging lane information input from the merging lane identification unit21 and the merged lane direction information input from the merged lanedirection identification unit 22.

In this case, for example, the following method is conceivable as amethod of determining whether or not the own vehicle driving lane is themerging lane to be performed by the own vehicle driving lanedetermination unit 23.

That is, when the merged lane direction contained in the merged lanedirection information is right, it follows that the own vehicle drivinglane is the leftmost lane, whereas when the merged lane directioncontained in the merged lane direction information is left, it followsthat the own vehicle driving lane is the rightmost lane. Thus, the ownvehicle driving lane determination unit 23 determines the position ofthe own vehicle driving lane based on the merged lane direction.

Then, when the position of the own vehicle driving lane is the same asthe position of the merging lane contained in the merging laneinformation, the own vehicle driving lane determination unit 23determines that the own vehicle driving lane is the merging lane. On theother hand, when the position of the own vehicle driving lane is not thesame as the position of the merging lane contained in the merging laneinformation, the own vehicle driving lane determination unit 23determines that the own vehicle driving lane is not the merging lane.

The own vehicle driving lane determination unit 23 generates a result ofdetermining whether or not the own vehicle driving lane is the merginglane as own vehicle driving lane information, and outputs this ownvehicle driving lane information to the own vehicle driving control unit24.

The vehicle condition detection unit 3 detects various kinds of signalsindicating vehicle conditions such as a vehicle speed, a steering wheelsteering angle, and a blinker signal indicating an ON/OFF switch stateof a blinker of the own vehicle, and outputs this detection result asvehicle condition information.

The forward vehicle detection unit 4 detects whether or not there is anyforward vehicle such as a four-wheel vehicle or a two-wheel vehicle thatis traveling ahead of the own vehicle, and also detects a distancebetween the own vehicle and the forward vehicle, and other suchinformation. The forward vehicle detection unit 4 outputs this detectionresult as forward vehicle information. Note that, the forward vehicledetection unit 4 is formed of, for example, one or a plurality of radarsmounted on a front body of the vehicle. Further, for example, amilliwave radar, an ultrasonic radar, or a laser radar may be used asthe radar.

The own vehicle driving control unit 24 controls the driving of the ownvehicle in accordance with the vehicle condition information acquiredfrom the vehicle condition detection unit 3 and the own vehicle drivinglane information input from the own vehicle driving lane determinationunit 23. The own vehicle driving control unit 24 includes a vehiclespeed control unit 25 as a specific example.

The vehicle speed control unit 25 performs vehicle speed control inaccordance with the vehicle condition information acquired from thevehicle condition detection unit 3, the forward vehicle informationacquired from the forward vehicle detection unit 4, and the own vehicledriving lane information input from the own vehicle driving lanedetermination unit 23 such that the distance between the own vehicle andthe forward vehicle is kept at a certain length or longer and at thesame time the vehicle speed is maintained at a set constant drive speed.

Specifically, when the own vehicle driving lane is determined not to bethe merging lane in the determination result contained in the ownvehicle driving lane information, the vehicle speed control unit 25determines control amounts for performing the vehicle speed control soas to keep the distance between the own vehicle and the forward vehicleat a certain length or longer and at the same time maintain the vehiclespeed at the set constant drive speed.

That is, in a case where the vehicle speed control is performed, thevehicle speed control unit 25 determines control amounts for realizingacceleration when the own vehicle needs to be accelerated, whereas thevehicle speed control unit 25 determines control amounts for realizingdeceleration when the own vehicle needs to be decelerated.

On the other hand, when the own vehicle driving lane is determined to bethe merging lane in the determination result contained in the ownvehicle driving lane information, the vehicle speed control unit 25determines control amounts for performing the vehicle speed control onthe premise that the acceleration operation of the own vehicle isprohibited.

That is, even when the own vehicle needs to be accelerated such as whenthe distance between vehicles is kept at a certain length or longer orwhen the vehicle speed is slower than the set constant drive speed, thevehicle speed control unit 25 prohibits the acceleration operation ofthe own vehicle and determines control amounts for keeping the currentvehicle speed. When the own vehicle needs to be decelerated, the vehiclespeed control unit 25 determines control amounts for realizingdeceleration.

Note that, the vehicle speed control unit 25 may be configured toperform vehicle speed control in accordance with the vehicle conditioninformation acquired from the vehicle condition detection unit 3 and theown vehicle driving lane information input from the own vehicle drivinglane determination unit 23 such that the vehicle speed is maintained ata set constant drive speed. Also in this case, when the own vehicledriving lane is determined to be the merging lane, the control amountsfor performing the vehicle speed control are determined on the premisethat the acceleration operation of the own vehicle is prohibited in thesame manner as described above.

Further, the vehicle speed control unit 25 determines whether or not theown vehicle has completed lane change from the merging lane to themerged lane based on the position of the own vehicle driving lanecontained in the own vehicle driving lane information, the steeringwheel steering angle signal or the blinker signal contained in thevehicle condition information, and the positions of the separation lineson both sides of the own vehicle driving lane contained in theseparation line information.

The prohibition of the acceleration operation is continued until the ownvehicle driving lane is determined not to be the merging lane or untilthe lane change is determined to have completed.

The engine control unit 5 controls an engine so as to achieve a torqueamount of the engine corresponding to the control amount determined bythe vehicle speed control unit 25

The brake control unit 6 controls a brake so as to achieve a brakestrength corresponding to the control amount determined by the vehiclespeed control unit 25

Next, a description is given of an operation of the driving assistanceapparatus according to the first embodiment with reference to FIG. 9 andFIG. 10. FIG. 9 and FIG. 10 are flowcharts for illustrating a series ofoperations of the driving assistance apparatus according to the firstembodiment of the present invention. Note that, FIG. 9 and FIG. 10 aretwo separate figures that form one flowchart, and thus the descriptionpart of FIG. 10 follows after the description part of FIG. 9.

In Step S101, the driving assistance control unit 2 determines whetheror not a power source ON signal is input. In Step S101, when the powersource ON signal is input, the driving assistance control unit 2proceeds to Step S102, whereas when the power source ON signal is notinput, the driving assistance control unit 2 executes processing of StepS101 again. Note that, the power source ON signal is input, for example,when the power source of the driving assistance apparatus is switchedfrom the OFF state to the ON state.

In Step S102, the merging lane identification unit 21 and the mergedlane direction identification unit 22 acquire the vehicle front imagefrom the image pickup unit 1, and the processing proceeds to Step S103.

In Step S103, the vehicle speed control unit 25 acquires the vehiclecondition information from the vehicle condition detection unit 3, andproceeds to Step S104.

In Step S104, the vehicle speed control unit 25 acquires the forwardvehicle information from the forward vehicle detection unit 4, and theprocessing proceeds to Step S105.

In Step S105, the merging lane identification unit 21 generates themerging lane information based on the vehicle front image acquired inStep S102, and the processing proceeds to Step S106.

In Step S106, the merged lane direction identification unit 22 generatesthe separation line information based on the vehicle front imageacquired in Step S102, and proceeds to Step S107.

In Step S107, the merged lane direction identification unit 22 generatesthe merged lane direction information based on the line types of theseparation lines on both sides of the own vehicle driving lane containedin the separation line information generated in Step S106, and theprocessing proceeds to Step S108.

In Step S108, the own vehicle driving lane determination unit 23generates the own vehicle driving lane information based on the merginglane information generated in Step S105 and the merged lane directioninformation generated in Step S107.

In Step S109, the vehicle speed control unit 25 determines whether ornot prohibition of the acceleration operation is currently selected. InStep S109, when the prohibition of the acceleration operation is notselected, the vehicle speed control unit 25 proceeds to Step S110,whereas when the prohibition of the acceleration operation is selected,the vehicle speed control unit 25 proceeds to Step S112.

In Step S110, the vehicle speed control unit 25 determines whether ornot the own vehicle driving lane is the merging lane based on thedetermination result contained in the own vehicle driving laneinformation generated in Step S108. In Step S110, when the own vehicledriving lane is the merging lane, the vehicle speed control unit 25proceeds to Step S111, whereas when the own vehicle driving lane is notthe merging lane, the vehicle speed control unit 25 proceeds to StepS115.

In Step S111, the vehicle speed control unit 25 selects prohibition ofthe acceleration operation, and proceeds to Step S115.

In Step S112, the vehicle speed control unit 25 determines whether ornot the lane change from the merging lane to the merged lane hascompleted based on the position of the own vehicle driving lanecontained in the own vehicle driving lane information generated in StepS108, the steering wheel steering angle signal or the blinker signalcontained in the vehicle condition information acquired in Step S103,and the positions of the separation lines on both sides of the ownvehicle driving lane contained in the separation line informationgenerated in Step S106. In Step S112, when the lane change has notcompleted, the vehicle speed control unit 25 proceeds to Step S113,whereas when the lane change has completed, the vehicle speed controlunit 25 proceeds to Step S114.

In Step S113, the vehicle speed control unit 25 continues the selectionof prohibition of the acceleration operation, and proceeds to Step S115.

In Step S114, the vehicle speed control unit 25 clears the selection ofprohibition of the acceleration operation, and proceeds to Step S115.

In Step S115, the vehicle speed control unit 25 determines whether ornot the prohibition of the acceleration operation is currently selected.In Step S115, when the prohibition of the acceleration operation is notselected, the vehicle speed control unit 25 proceeds to Step S116,whereas when the prohibition of the acceleration operation is selected,the vehicle speed control unit 25 proceeds to Step S117.

In Step S116, the vehicle speed control unit 25 determines controlamounts for performing the vehicle speed control based on the vehiclespeed contained in the vehicle condition information acquired in StepS103 and the forward vehicle information acquired in Step S104 such thatthe distance between the own vehicle and the forward vehicle is kept ata certain length or longer and at the same time the vehicle speed ismaintained at a set constant drive speed, and the processing proceeds toStep S118. At this stage, in a case where the prohibition of theacceleration operation is not selected, the vehicle speed control unit25 determines control amounts for realizing acceleration when the ownvehicle needs to be accelerated, whereas the vehicle speed control unit25 determines control amounts for realizing deceleration when the ownvehicle needs to be decelerated.

In Step S117, the vehicle speed control unit 25 determines controlamounts for performing the vehicle speed control based on the vehiclespeed contained in the vehicle condition information acquired in StepS103 and the forward vehicle information acquired in Step S104 such thatthe distance between the own vehicle and the forward vehicle is kept ata certain length or longer and at the same time the vehicle speed ismaintained at a set constant drive speed, and the processing proceeds toStep S118. At this stage, in a case where the prohibition of theacceleration operation is selected, the vehicle speed control unit 25determines control amounts for keeping the current vehicle speed withoutperforming the acceleration operation even when the own vehicle needs tobe accelerated, whereas the vehicle speed control unit 25 determinescontrol amounts for realizing deceleration when the own vehicle needs tobe decelerated.

In Step S118, the engine control unit 5 controls the engine such thatthe engine has torque whose amount corresponds to the control amountdetermined in Step S116 or in Step S117, and the processing proceeds toStep S119.

In Step S119, the brake control unit 6 controls the brake such that thebrake strength corresponds to the control amount determined in Step S116or in Step S117, and the processing proceeds to Step S120.

In Step S120, the driving assistance control unit 2 determines whetheror not a power source OFF signal is input. In Step S120, when the powersource OFF signal is input, the driving assistance control unit 2 endsthe series of processing steps, whereas when the power source OFF signalis not input, the driving assistance control unit 2 returns to Step S102and executes processing from Step S102 again. Note that, the powersource OFF signal is input, for example, when the power source of thedriving assistance apparatus is switched from the ON state to the OFFstate.

As described above, according to the first embodiment, the drivingassistance apparatus is configured to determine whether or not the ownvehicle driving lane is the merging lane based on the result ofidentifying the merging lane from a lane reduction sign detected in avehicle front image and the result of identifying the merged lanedirection with respect to the own vehicle driving lane from separationlines on both sides of the own vehicle driving lane that are detected inthe vehicle front image, and to control the driving of the own vehiclein accordance with the determination result and the vehicle conditioninformation of the own vehicle. With this, it is possible to provideappropriate driving assistance to the driver of a vehicle traveling on amerging lane.

Further, as one way of controlling the driving of the own vehicle, thedriving assistance apparatus is configured to perform the vehicle speedcontrol such that the vehicle speed contained in the vehicle conditioninformation is the set speed, and when the own vehicle driving lane isdetermined to be the merging lane, prohibit the acceleration operationof the own vehicle in the vehicle speed control. With this, it ispossible to prevent the own vehicle from performing the accelerationoperation despite the lane reduction during traveling on the merginglane.

Further, as another way of controlling the driving of the own vehicle,the driving assistance apparatus is configured to perform the vehiclespeed control such that the distance between the own vehicle and theforward vehicle contained in the forward vehicle information is kept ata certain length or longer and at the same time the vehicle speedcontained in the vehicle condition information is maintained at a setspeed, and when the own vehicle driving lane is determined to be themerging lane, prohibit the acceleration operation of the own vehicle inthe vehicle speed control. With this, it is possible to prevent the ownvehicle from performing the acceleration operation during traveling onthe merging lane when the forward vehicle has changed the lane and thereis no vehicle ahead.

Second Embodiment

In a second embodiment of the present invention, a description is givenof a driving assistance apparatus including the own vehicle drivingcontrol unit 24 having a configuration different from that of the firstembodiment. Note that, in the second embodiment, the description of thesame points as those of the first embodiment is omitted, and pointsdifferent from those of the first embodiment are mainly described.

FIG. 11 is an overall block diagram for illustrating a drivingassistance apparatus according to the second embodiment of the presentinvention. The driving assistance apparatus of FIG. 11 includes theimage pickup unit 1, the driving assistance control unit 2, and thevehicle condition detection unit 3. In FIG. 11, a steering wheel controlunit 7, an audio output unit 8, and a speaker 9 to be controlled by thedriving assistance control unit 2 are illustrated together with theabove-mentioned components.

The driving assistance control unit 2 includes the merging laneidentification unit 21, the merged lane direction identification unit22, the own vehicle driving lane determination unit 23, and the ownvehicle driving control unit 24. Further, the own vehicle drivingcontrol unit 24 is formed of a steering assistance control unit 26 and alane departure determination unit 27.

The own vehicle driving lane determination unit 23 generates the ownvehicle driving lane information in the same way as in the firstembodiment, and outputs an alarm instruction signal to the audio outputunit 8 when determining that the own vehicle driving lane is the merginglane.

Thus, it is possible for the driver to change the lane in an unhurriedway by configuring the own vehicle driving lane determination unit 23such that when the own vehicle driving lane is determined to be themerging lane, the driver is warned of this determination.

The steering assistance control unit 26 provides steering assistancecorresponding to a mode based on the vehicle condition informationacquired from the vehicle condition detection unit 3, the separationline information input from the merged lane direction identificationunit 22, and the own vehicle driving lane information input from the ownvehicle driving lane determination unit 23.

Specifically, the steering assistance control unit 26 determines asteering force of the steering wheel for realizing steering assistancecontrol in a normal mode when the own vehicle driving lane is determinednot to be the merging lane in the determination result contained in theown vehicle driving lane information.

That is, the steering assistance control unit 26 determines a steeringforce of the steering wheel for realizing steering assistance thatintends to move the own vehicle back to the center side of the ownvehicle driving lane when the own vehicle travels toward any one ofseparation lines on both sides of the own vehicle driving lane so thatthe own vehicle keeps traveling between the separation lines on bothsides thereof.

On the other hand, the steering assistance control unit 26 determines asteering force of the steering wheel for realizing steering assistancecontrol in a specified mode when the own vehicle driving lane isdetermined to be the merging lane in the determination result containedin the own vehicle driving lane information.

That is, the steering assistance control unit 26 determines a steeringforce of the steering wheel to be invalid so as not to provide thesteering assistance that intends to move the own vehicle back to thecenter side of the own vehicle driving lane, even when the own vehicletravels toward the merged lane side, which is one side of the separationlines on both sides of the own vehicle driving lane. On the other hand,the steering assistance control unit 26 determines a steering force ofthe steering wheel for realizing steering assistance that intends tomove the own vehicle back to the center side of the own vehicle drivinglane when the own vehicle travels toward the other side of theseparation lines on both sides of the own vehicle driving lane.

In this way, the steering assistance control unit 26 performs thesteering assistance control such that the own vehicle keeps traveling onthe own vehicle driving lane. Further, when the own vehicle driving laneis determined to be the merging lane as a result of determination by theown vehicle driving lane determination unit 23, the steering assistancecontrol unit 26 determines whether or not to perform the steeringassistance control depending on toward which side of the separationlines on both sides of the own vehicle driving lane the own vehicletravels.

When the own vehicle travels toward the merged lane side, which is oneside of the separation lines on both sides of the own vehicle drivinglane, the steering assistance control unit 26 does not perform thesteering assistance control. On the other hand, when the own vehicletravels toward the other side of the separation lines on both sides ofthe own vehicle driving lane, the steering assistance control unit 26performs the steering assistance control.

Note that, the steering assistance control in the specified mode iscontinued until the own vehicle driving lane is determined not to be themerging lane or until the lane change is determined to have completed.

The lane departure determination unit 27 performs a lane departuredetermination corresponding to a mode based on the vehicle conditioninformation acquired from the vehicle condition detection unit 3, theseparation line information input from the merged lane directionidentification unit 22, and the own vehicle driving lane informationinput from the own vehicle driving lane determination unit 23.

Specifically, the lane departure determination unit 27 performs a lanedeparture determination in a normal mode when the own vehicle drivinglane is determined not to be the merging lane in the determinationresult contained in the own vehicle driving lane information.

That is, the lane departure determination unit 27 determines whether ornot there is a departure possibility of the own vehicle departing fromthe own vehicle driving lane, and when determining that there is adeparture possibility, outputs an alarm instruction signal to the audiooutput unit 8.

On the other hand, the lane departure determination unit 27 performs alane departure determination in a specified mode when the own vehicledriving lane is determined to be the merging lane in the determinationresult contained in the own vehicle driving lane information.

That is, the lane departure determination unit 27 determines, in thesame way as in the normal mode, whether or not there is a departurepossibility of the own vehicle departing from the own vehicle drivinglane. However, even in a case where the lane departure determinationunit 27 determines that there is a departure possibility, the lanedeparture determination unit 27 does not output an alarm instructionsignal to the audio output unit 8 when the own vehicle departs from theown vehicle driving lane toward a separation line on the merged laneside of the separation lines on both sides of the own vehicle drivinglane.

In this way, the lane departure determination unit 27 determines whetheror not there is a departure possibility of the own vehicle departingfrom the own vehicle driving lane, and when determining that there is adeparture possibility, gives a warning to the driver. Further, when theown vehicle driving lane is determined to be the merging lane as aresult of determination by the own vehicle driving lane determinationunit 23, the lane departure determination unit 27 determines whether ornot to give a warning depending on toward which side of the separationlines on both sides of the own vehicle driving lane there is apossibility of the own vehicle departing from the own vehicle drivinglane.

That is, when there is a possibility of the own vehicle departing fromthe own vehicle driving lane toward the merged lane side, which is oneside of the separation lines on both sides of the own vehicle drivinglane, the lane departure determination unit 27 does not give a warning.On the other hand, when there is a possibility of the own vehicledeparting from the own vehicle driving lane toward the other side of theseparation lines on both sides of the own vehicle driving lane, the lanedeparture determination unit 27 gives a warning.

Note that, the lane departure determination in the specified mode iscontinued until the own vehicle driving lane is determined not to be themerging lane or until the lane change is determined to have completed.

The steering wheel control unit 7 controls the steering wheel so as toachieve the steering force of the steering wheel determined by thesteering assistance control unit 26.

When an alarm instruction signal is input from at least one of the ownvehicle driving lane determination unit 23 or the lane departuredetermination unit 27, the audio output unit 8 outputs a warning soundusing the speaker 9.

Next, a description is given of an operation of the driving assistanceapparatus according to the second embodiment with reference to FIG. 12and FIG. 13. FIG. 12 and FIG. 13 are flowcharts for illustrating aseries of operations of the driving assistance apparatus according tothe second embodiment of the present invention.

Note that, FIG. 12 and FIG. 13 are two separate figures that form oneflowchart, and thus the description part of FIG. 13 follows after thedescription part of FIG. 12. Further, each processing step of from StepS201 to Step S207 in FIG. 12 is the same as that of from Step S101 toStep S103 and from Step S105 to Step S108 in FIG. 9. Thus, a descriptionthereof is omitted and processing steps from Step S208 are described.

In Step S208, the own vehicle driving control unit 24 determines whetheror not the specified mode is currently selected. In Step S208, when thespecified mode is not selected, the own vehicle driving control unit 24proceeds to Step S209, whereas when the specified mode is selected, theown vehicle driving control unit 24 proceeds to Step S211.

In Step S209, the own vehicle driving control unit 24 determines whetheror not the own vehicle driving lane is the merging lane based on thedetermination result contained in the own vehicle driving laneinformation generated in Step S207. In Step S209, when the own vehicledriving lane is the merging lane, the own vehicle driving control unit24 proceeds to Step S210, whereas when the own vehicle driving lane isnot the merging lane, the own vehicle driving control unit 24 proceedsto Step S214.

In Step S210, the own vehicle driving control unit 24 selects thespecified mode and proceeds to Step S214.

In Step S211, the own vehicle driving control unit 24 determines whetheror not the lane change from the merging lane to the merged lane hascompleted based on the position of the own vehicle driving lanecontained in the own vehicle driving lane information generated in StepS207, the steering wheel steering angle signal or the blinker signalcontained in the vehicle condition information acquired in Step S203,and the positions of the separation lines on both sides of the ownvehicle driving lane contained in the separation line informationgenerated in Step S205. In Step S211, when the lane change has notcompleted, the own vehicle driving control unit 24 proceeds to StepS212, whereas when the lane change has completed, the own vehicledriving control unit 24 proceeds to Step S213.

In Step S212, the own vehicle driving control unit 24 continues theselection of the specified mode and proceeds to Step S214.

In Step S213, the own vehicle driving control unit 24 clears theselection of the specified mode and proceeds to Step S214.

In Step S214, the own vehicle driving control unit 24 determines whetheror not the specified mode is currently selected. In Step S214, when thespecified mode is not selected, the own vehicle driving control unit 24proceeds to Step S215, whereas when the specified mode is selected, theown vehicle driving control unit 24 proceeds to Step S217.

In Step S215, the own vehicle driving control unit 24 determines asteering force of the steering wheel for performing the steeringassistance control in the normal mode, and proceeds to Step S216.

In Step S216, the own vehicle driving control unit 24 performs the lanedeparture determination in the normal mode, and the processing proceedsto Step S219.

In Step S217, the own vehicle driving control unit 24 determines asteering force of the steering wheel for performing the steeringassistance control in the specified mode, and proceeds to Step S218.

In Step S218, the own vehicle driving control unit 24 performs the lanedeparture determination in the specified mode, and the processingproceeds to Step S219.

In Step S219, the steering wheel control unit 7 controls the steeringwheel so as to achieve the steering force of the steering wheeldetermined in Step S215 or Step S217, and the processing proceeds toStep S220.

In Step S220, the audio output unit 8 determines whether or not thealarm instruction signal is input. In Step S220, when the alarminstruction signal is input, the audio output unit 8 proceeds to StepS221, whereas when the alarm instruction signal is not input, the audiooutput unit 8 proceeds to Step S222.

In Step S221, the audio output unit 8 outputs a warning sound using thespeaker 9, and the processing proceeds to Step S222.

In Step S222, the driving assistance control unit 2 determines whetheror not the power source OFF signal is input. In Step S222, when thepower source OFF signal is input, the driving assistance control unit 2ends the series of processing steps, whereas when the power source OFFsignal is not input, the driving assistance control unit 2 returns toStep S202 and executes processing from Step S202 again.

As described above, according to the second embodiment, the drivingassistance apparatus is configured to determine, when the own vehicledriving lane is determined to be the merging lane, whether or not toperform the steering assistance control depending on toward which sideof the separation lines on both sides of the own vehicle driving lanethe own vehicle travels. With this, it is possible to continue toperform appropriate steering assistance control for the driver of avehicle traveling on a merging lane because the steering assistancecontrol is not performed when the vehicle traveling on the merging lanemerges into a merged lane from the merging lane.

Further, the driving assistance apparatus is configured to determine,when the own vehicle driving lane is determined to be the merging lane,whether or not to give a warning depending on toward which side of theseparation lines on both sides of the own vehicle driving lane there isa possibility of the own vehicle departing from the own vehicle drivinglane. With this, it is possible to continue to give an appropriatewarning to the driver of a vehicle traveling on a merging lane becausethe warning is not given to the driver when the vehicle traveling on themerging lane merges into a merged lane from the merging lane.

Note that, descriptions are given of the first and second embodimentsindividually, but configuration examples described respectively in thefirst and second embodiments can arbitrary be combined.

What is claimed is:
 1. A driving assistance apparatus, comprising: acamera configured to generate a vehicle front image by picking up animage of a front field of an own vehicle traveling on an own vehicledriving lane; and a processor implementing: a merging laneidentification unit configured to detect a lane reduction sign in thevehicle front image generated by the camera, and identify a merginglane, based on the lane reduction sign, to generate merging laneinformation; a merged lane direction identification unit configured todetect separation lines on both sides of the own vehicle driving lane inthe vehicle front image generated by the camera, and identify a mergedlane direction with respect to the own vehicle driving lane, based onthe separation lines on both sides, to generate merged lane directioninformation; an own vehicle driving lane determination unit configuredto determine whether or not the own vehicle driving lane is the merginglane, based on the merging lane information generated by the merginglane identification unit and the merged lane direction informationgenerated by the merged lane direction identification unit; a vehiclecondition detection unit configured to detect vehicle conditioninformation of the own vehicle; and an own vehicle driving control unitconfigured to control driving of the own vehicle in accordance with thevehicle condition information detected by the vehicle conditiondetection unit and a result of whether or not the own vehicle drivinglane is the merging lane that is determined by the own vehicle drivinglane determination unit, wherein the own vehicle driving control unitcomprises a vehicle speed control unit configured to: perform vehiclespeed control to maintain a vehicle speed included in the vehiclecondition information detected by the vehicle condition detection unit,at a set speed; and prohibit, in response to the own vehicle drivinglane being determined to be the merging lane, an acceleration operationof the own vehicle in performing the vehicle speed control.
 2. Thedriving assistance apparatus according to claim 1, wherein the merginglane identification unit is further configured to identify the merginglane, based on a shape of a figure that is depicted in the lanereduction sign detected in the vehicle front image.
 3. The drivingassistance apparatus according to claim 1, further comprising a radarconfigured to detect forward vehicle information of a forward vehicletraveling ahead of the own vehicle, wherein the vehicle speed controlunit is further configured to perform the vehicle speed control to keepa distance between the own vehicle and the forward vehicle at a lengthor longer, while maintaining the vehicle speed at the set speed, thedistance being included in the forward vehicle information detected bythe radar.
 4. The driving assistance apparatus according to claim 1,wherein the own vehicle driving control unit comprises a steeringassistance control unit configured to: perform steering assistancecontrol to cause the own vehicle to keep traveling on the own vehicledriving lane; and in response to the own vehicle driving lane beingdetermined to be the merging lane: avoid performing the steeringassistance control in response to the own vehicle traveling toward amerged lane side that is one side of the separation lines on both sides;and perform the steering assistance control in response to the ownvehicle traveling toward another side of the separation lines on bothsides.
 5. The driving assistance apparatus according to claim 1, whereinthe own vehicle driving control unit comprises a lane departuredetermination unit configured to: determine whether or not there is adeparture possibility of the own vehicle departing from the own vehicledriving lane; give a warning in response to the departure possibilitybeing determined; and in response to the own vehicle driving lane beingdetermined to be the merging lane: avoid giving the warning in responseto there being a possibility of the own vehicle departing from the ownvehicle driving lane toward a merged lane side that is one side of theseparation lines on both sides; and give the warning in response tothere being a possibility of the own vehicle departing from the ownvehicle driving lane toward another side of the separation lines on bothsides.
 6. The driving assistance apparatus according to claim 1, whereinthe own vehicle driving lane determination unit is further configured togive a warning in response to the own vehicle driving lane beingdetermined to be the merging lane.
 7. A driving assistance method,comprising: generating a vehicle front image by picking up an image of afront field of an own vehicle traveling on an own vehicle driving lane;detecting a lane reduction sign in the vehicle front image that isgenerated; identifying a merging lane, based on the lane reduction sign,to generate merging lane information; detecting separation lines on bothsides of the own vehicle driving lane in the vehicle front image that isgenerated; identifying a merged lane direction with respect to the ownvehicle driving lane, based on the separation lines on both sides, togenerate merged lane direction information; determining whether or notthe own vehicle driving lane is the merging lane, based on the merginglane information that is generated and the merged lane directioninformation that is generated; controlling driving of the own vehicle inaccordance with vehicle condition information of the own vehicle and aresult of whether or not the own vehicle driving lane is the merginglane that is determined; performing vehicle speed control to maintain avehicle speed included in the vehicle condition information that isdetected, at a set speed; and prohibiting, in response to the ownvehicle driving lane being determined to be the merging lane, anacceleration operation of the own vehicle in performing the vehiclespeed control.
 8. The driving assistance apparatus according to claim 1,wherein the vehicle speed control unit is further configured to:determine whether or not a lane change from the merging lane to a mergedlane is completed, based on a position of the own vehicle driving lane,a steering wheel steering angle signal or a blinker signal included inthe vehicle condition information, and positions of the separation lineson both sides; in response to the lane change being determined to becompleted, clear the acceleration operation of the own vehicle frombeing prohibited; and in response to the lane change being determined tobe not completed, continue the prohibiting of the acceleration operationof the own vehicle.
 9. A driving assistance apparatus, comprising: acamera configured to generate a vehicle front image by picking up animage of a front field of an own vehicle traveling on an own vehicledriving lane; and a processor implementing: a merging laneidentification unit configured to detect a lane reduction sign in thevehicle front image generated by the camera, and identify a merginglane, based on the lane reduction sign, to generate merging laneinformation; a merged lane direction identification unit configured todetect separation lines on both sides of the own vehicle driving lane inthe vehicle front image generated by the camera, and identify a mergedlane direction with respect to the own vehicle driving lane, based onthe separation lines on both sides, to generate merged lane directioninformation; an own vehicle driving lane determination unit configuredto determine whether or not the own vehicle driving lane is the merginglane, based on the merging lane information generated by the merginglane identification unit and the merged lane direction informationgenerated by the merged lane direction identification unit; a vehiclecondition detection unit configured to detect vehicle conditioninformation of the own vehicle; and an own vehicle driving control unitconfigured to control driving of the own vehicle in accordance with thevehicle condition information detected by the vehicle conditiondetection unit and a result of whether or not the own vehicle drivinglane is the merging lane that is determined by the own vehicle drivinglane determination unit, wherein the own vehicle driving control unitcomprises a vehicle speed control unit configured to prohibit, inresponse to the own vehicle driving lane being determined to be themerging lane, an acceleration operation of the own vehicle in performinga vehicle speed control.
 10. A driving assistance apparatus, comprising:a camera configured to generate a vehicle front image by picking up animage of a front field of an own vehicle traveling on an own vehicledriving lane; and a processor implementing: a merging laneidentification unit configured to detect a lane reduction sign in thevehicle front image generated by the camera, and identify a merginglane, based on the lane reduction sign, to generate merging laneinformation; a merged lane direction identification unit configured todetect separation lines on both sides of the own vehicle driving lane inthe vehicle front image generated by the camera, and identify a mergedlane direction with respect to the own vehicle driving lane, based onthe separation lines on both sides, to generate merged lane directioninformation; an own vehicle driving lane determination unit configuredto determine whether or not the own vehicle driving lane is the merginglane, based on the merging lane information generated by the merginglane identification unit and the merged lane direction informationgenerated by the merged lane direction identification unit; a vehiclecondition detection unit configured to detect vehicle conditioninformation of the own vehicle; and an own vehicle driving control unitconfigured to control driving of the own vehicle in accordance with thevehicle condition information detected by the vehicle conditiondetection unit and a result of whether or not the own vehicle drivinglane is the merging lane that is determined by the own vehicle drivinglane determination unit, wherein the own vehicle driving control unitcomprises a vehicle speed control unit configured to: determine whetheror not a lane change from the merging lane to a merged lane iscompleted, based on a position of the own vehicle driving lane, asteering wheel steering angle signal or a blinker signal included in thevehicle condition information, and positions of the separation lines onboth sides; in response to the lane change being determined to becompleted, clear an acceleration operation of the own vehicle from beingprohibited; and in response to the lane change being determined to benot completed, continue a prohibiting of the acceleration operation ofthe own vehicle.
 11. A driving assistance method, comprising: generatinga vehicle front image by picking up an image of a front field of an ownvehicle traveling on an own vehicle driving lane; detecting a lanereduction sign in the vehicle front image that is generated; identifyinga merging lane, based on the lane reduction sign, to generate merginglane information; detecting separation lines on both sides of the ownvehicle driving lane in the vehicle front image that is generated;identifying a merged lane direction with respect to the own vehicledriving lane, based on the separation lines on both sides, to generatemerged lane direction information; determining whether or not the ownvehicle driving lane is the merging lane, based on the merging laneinformation that is generated and the merged lane direction informationthat is generated; controlling driving of the own vehicle in accordancewith vehicle condition information of the own vehicle and a result ofwhether or not the own vehicle driving lane is the merging lane that isdetermined; and prohibiting, in response to the own vehicle driving lanebeing determined to be the merging lane, an acceleration operation ofthe own vehicle in performing a vehicle speed control.
 12. A drivingassistance method, comprising: generating a vehicle front image bypicking up an image of a front field of an own vehicle traveling on anown vehicle driving lane; detecting a lane reduction sign in the vehiclefront image that is generated; identifying a merging lane, based on thelane reduction sign, to generate merging lane information; detectingseparation lines on both sides of the own vehicle driving lane in thevehicle front image that is generated; identifying a merged lanedirection with respect to the own vehicle driving lane, based on theseparation lines on both sides, to generate merged lane directioninformation; determining whether or not the own vehicle driving lane isthe merging lane, based on the merging lane information that isgenerated and the merged lane direction information that is generated;controlling driving of the own vehicle in accordance with vehiclecondition information of the own vehicle and a result of whether or notthe own vehicle driving lane is the merging lane that is determined;determining whether or not a lane change from the merging lane to amerged lane is completed, based on a position of the own vehicle drivinglane, a steering wheel steering angle signal or a blinker signalincluded in the vehicle condition information, and positions of theseparation lines on both sides; clearing, in response to the lane changebeing determined to be completed, an acceleration operation of the ownvehicle from being prohibited; and continuing, in response to the lanechange being determined to be not completed, a prohibiting of theacceleration operation of the own vehicle.